Reflex Camera Mirror Arrangement Space Reduction
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Solution Overview
Problem
The existing mirror arrangements in reflex cameras face challenges in maintaining precise autofocus detection while trying to reduce the installation space for the main mirror, as the secondary mirror's position is affected by the complex movement path of the main mirror, especially when using a four-bar linkage, leading to misalignment and increased mechanical complexity.
Innovation Solution
The secondary mirror is mounted rotatably about a spindle parallel to the main mirror's spindle and driven via a connecting lug or curved disk from the main mirror's driving crank, allowing independent movement and reducing the number of components, with residual play and a spring mechanism ensuring accurate positioning and light blocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the main mirror is mounted on a four-bar linkage to reduce installation space, then the installation space for the main mirror is shortened, but the secondary mirror becomes misaligned due to the complex movement path
Solution Approach 1:
The patent separates the mounting of the secondary mirror from the main mirror assembly. The secondary mirror is mounted on a separate carrier that is independently pivotable on a spindle fixed to the housing, rather than being coupled to the main mirror's four-bar linkage movement. This segmentation allows the secondary mirror to maintain its position accuracy independent of the main mirror's complex motion path.
Solution Approach 2:
The patent introduces an intermediary connecting lug that couples the secondary mirror carrier to the main mirror assembly. This connecting lug allows the secondary mirror to be driven by the main mirror's movement while maintaining independent pivot capability, thus mediating between the space-saving main mirror linkage and the position-accuracy requirement of the secondary mirror.
2Device complexity
If the secondary mirror is mounted on the main mirror, then the structure is simplified, but the secondary mirror position is affected by the main mirror's movement path
Solution Approach 1:
The patent divides the mounting structure into separate components: the main mirror assembly and the secondary mirror carrier. The secondary mirror carrier is mounted on a separate spindle fixed to the housing, creating an independent mounting path that does not transmit movement errors from the main mirror to the secondary mirror.
Solution Approach 2:
The patent combines the secondary mirror carrier with the main mirror assembly through the connecting lug, allowing both mirrors to be actuated by the same driving mechanism while maintaining independent pivot capabilities. This merging achieves structural efficiency without compromising position accuracy.
3Volume of moving object
If a four-bar linkage is used for the main mirror, then the installation space is reduced, but the mechanical complexity increases
Solution Approach 1:
The patent segments the mirror system into independently mounted components. The main mirror uses a four-bar linkage for space-saving operation, while the secondary mirror is mounted on a separate carrier with its own spindle. This segmentation allows each component to be optimized independently, reducing overall mechanical complexity despite the four-bar linkage.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution maintains the precision of single main-mirror mounting with reduced installation space, comparable component count, and simplified mechanical complexity, ensuring accurate autofocus detection and light management without additional measures for stray light prevention.
Implementation Method 1
the light coming from the objective is projected onto a matte focusing screen via a main mirror... Through a partially transmissive zone in the main mirror, a second detail image of the recording object is formed... via a secondary mirror that is pivotably mounted on the main mirror
Implementation Method 2
residual play and a spring mechanism ensuring accurate positioning and light blocking
Data Source
AI summary
A mirror arrangement for reflex cameras is provided. A main mirror is pivotably connected to a steering lever, which is rotatable about a rotary spindle, such that the main mirror is pivoted and lowered during transition into the lower position. A secondary mirror is rotatably mounted to a housing via a pivot arm that is arranged pivotably about a rotary spindle that is fixed to the housing. The rotary spindle of the pivot arm is parallel to the rotary spindle of the steering lever. The mirror arrangement further comprises an actuating lever, which is connected to the main mirror and the pivot arm of the secondary mirror. The actuating lever is configured to provide simultaneous movement of the main mirror and of the secondary mirror from the upper position into the lower position and vice versa.